With rolling element cages of this type, in order to avoid asymmetries and resulting imbalances as well as sharp-edged projections that can come to rest against the applicable running partner of the cage, for example an outer bearing ring, the rolling element cages are manufactured in such a way that the ends of the strip sections are joined together without any axial or radial offset to the greatest degree possible, which is to say that the cages are rotationally symmetrical as well as radially and axially smooth. A mandrel, for example, is used for this purpose (or, according to DE 10 2007 044,946 A1, the crankshaft journal that is to accommodate the rolling bearing); the bent strip section is placed thereon in such a manner that the strip section ends rest flush against one another, and these ends are welded thereon in an offset-free manner.
In the past, as long as rolling element cages could not be produced so as to be fully smooth at least radially and axially, care was taken to ensure that the weld seam regions could not come into direct contact with associated opposing parts.
Thus, DE 1,675,083 A1 discloses a cage for a radial needle bearing or radial roller bearing of the type specified in the preamble of claim 1, in which the ends of the edges (rims) joined together by welding are for their part offset radially in a direction opposite to the radial offset of the edges, so that the weld seam on one side of the cage is radially recessed from the corresponding cylindrical surface. This design of the cage achieves the result that only undistorted regions ensure centering of the cage on the adjacent race, without the weld seam being able to come into contact with the race.
However, it has been shown that with a symmetrical and smooth design of the cage, in many cases a disadvantageous lubricating oil distribution is established and cannot be influenced in any way. Especially in the case of bearings with lubricant starvation and slow rotational motions, in some technical applications a different oil distribution is desired in the bearing than is actually taking place. In bearings with grease lubrication, especially if they run very infrequently, it is possible for the grease to be forced out of the rolling contact over time, and no longer return to the rolling contact in sufficient quantity even during operation, which can lead to early bearing damage.
Furthermore, the vibration characteristics of absolutely rotationally symmetrical rolling element cages, and thus their influence on the vibration characteristics of the overall system, are fixed by the symmetry, which in some cases results in suboptimal system characteristics.